JPH0474192B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to automatic adjustment of print position during reciprocating printing of a serial printer. Many serial printers use a rotary encoder coaxially attached to a drive motor as a position detector. This is because it is cheaper than using a linear encoder or the like that directly detects the print position, and the detection resolution can be relatively high. However, since the drive source is decelerated by a gear and the printing part is moved linearly via a belt, rope, etc., the detected position may differ from the actual position depending on the direction of movement due to the bump of the deceleration gear or the elongation of the belt or rope. Therefore, when performing back-and-forth printing to increase the printing speed, the position of the print on the print paper will shift even if the print is performed at the same timing of the position signal. Therefore, a method has been adopted in which the printing position is corrected by delaying or advancing one of the printing timing signals in consideration of the moving direction of the printing section. However, with this method, as the printer is used, the print position shifts due to increased backlash due to wear of the gears and stretching of the belt or rope, which requires re-correction. In order to eliminate such drawbacks, the present invention proposes the following method. When the printer is powered on, the printing section (printing section, carriage) is moved back and forth, and the deviation of the position signal when the printing section passes an index provided on the movement path is detected and calculated. This value changes the delay interval (time) of the print timing signal,
Automatically adjust the print position. Next, the present invention will be explained in detail using the figures. Figure 1 shows the structure of a general serial printer, in which the output of a drive motor 1 is connected to a reduction gear 2,
3 to the drive pulley 4. The driving pulley 4 and the driven pulley 5 are connected by a rope (or timing belt, etc.) 6, and as the driving pulley 4 rotates, the carriage 7 carrying the print head 8 is moved along the guide shafts 9, 10 in the direction of the arrow. 11 is moved in a straight line. The output waveform of the rotary encoder 12 mounted coaxially with the drive motor 1 at this time is shown in FIG. The figure shows the case where there is no extension of the rope (or belt) and no backlash of the reduction gear, and two phase signals (A phase and B phase) with a 1/4 pitch shift are used to determine the direction of carriage movement. Output. These two-phase encoder signals are counted by an addition/subtraction counter, and when the figure moves from left to right, the position N is counted at point 21, and when it moves from right to left, the position N is counted at point 25. Ru. FIG. 3 shows the encoder signal when there is a backlash in the reduction gear or an extension in the rope (belt). The encoder signal 31 is the one when the traveling direction is displaced from left to right on the drawing. Based on this displacement signal, the encoder signal from right to left when the initial backlash etc. is adjusted to a small value is as shown in 32. , and is detected with a position error 34. On the other hand, if the reduction gear wears out or the rope (belt) stretches, the displacement signal from right to left will have an error of 35
is detected as the encoder signal 33. By measuring the error signals 34 and 35 and correcting the printing timing signal using the difference between these signals as a correction value, it is possible to correct errors in printing position due to printing direction. Next, an example of automatic correction will be described. Since the encoder described here outputs a displacement signal as a pulse train, it is impossible to detect an absolute position. Therefore, the origin of displacement is placed on the carriage running path, and when the carriage passes this origin, the value of the addition/subtraction counter that counts the encoder signal is reset, so that the value of the addition/subtraction counter represents the displacement from this origin. As shown in FIG. 1, this origin signal is generated by a reset detector 17 and a shield flag 18 mounted on the carriage. FIG. 4 is a circuit diagram of this embodiment. Encoder signal 42, 4
3 is shaped into edge pulses 49 to 52 corresponding to all edges by mono multivibrator 44 to 47. This edge pulse is separated in direction by a gate circuit 53 and inputted as an addition pulse 57 and a subtraction pulse 58 to an addition/subtraction counter 68. At this time, the resolution control signal 6 output from the control microcomputer 54
5, the addition/subtraction counter 68 can count with four times the resolution. It is assumed that when the printer loses power, the shielding flag 18 attached to the carriage 7 first intercepts the reset detector 17, and the reset detector 17 outputs a signal indicating that the carriage 7 is at the home position. do. In this state, the carriage is moved from left to right, and the mono multivibrator 60 converts the product of the reset detector signal 41 and the output signal 59 of the flip-flop 48 for direction determination into an edge signal 61, and this signal is used to control the addition/subtraction counter. Reset. As a result, when the carriage moves from left to right, the addition/subtraction counter is reset at the position where the shielding flag 18 passes through the reset detector. At this time, the resolution control signal 65 from the control microcomputer is set to four times the resolution, and subsequent correction value counting is performed. Next, the carriage is moved to the right, reversed and moved to the left, and the value 62 of the addition/subtraction counter at the moment when the shielding flag 18 crosses the reset detector 17 is read into the control microcomputer 54 and the correction value α shall be. Furthermore, there is a delay in the printing head from when the print timing signal is applied until it actually prints. Therefore, this delay amount is set with the switch 63, and the correction amount β (64)
The control microcomputer 54 is loaded with this information in advance. The actual correction amount γ is γ=α
+β becomes. When printing is to be performed, the resolution control signal 65 is set to 1x resolution. The print timing edge change circuit 69 receives the print timing edge change signal 6.
6 and 67, a circuit that changes the edge of the print timing 55 from 21 to 25 corrects the lower digits (2 bits) of the correction amount. For example, as shown in FIG. 3, it is assumed that the encoder signal is 31 when the printing direction is from left to right, and 33 when the printing direction is from right to left. When the reset signal is detected at position 36, the value of the correction amount α is detected as -5. Assuming that β is 0 and position N is the printing position, printing is performed at the first position 37 in the printing direction from left to right in the advancing direction of section N. In the printing direction from right to left, the last position in the advancing direction of time interval N where the correction value is 0 is the printing position, but since the correction value is detected as -5, γ/4 = -5/4 = Printing is performed at a position offset by -11/4, that is, at a position further offset by -1/4 from the last position in the advancing direction of section N-1. This is done by opening the printing gate 71 with the printing control signal 70 in section N-1 and further setting the printing timing edge change signals 66 and 67 to 0 and 0, respectively.
A print timing change signal 56 is obtained at the position. Table 1 shows the relationship between the correction value γ/4 and the edge change signals 66 and 67.

[Table] In the above position correction method for reciprocating printing (reciprocating printing) of the present invention, the backlash of the reduction gear of the carriage drive motor increases due to wear of the gear, or the rope or belt that moves the carriage linearly increases. When the length increases due to changes over the years, this amount is automatically measured at a resolution four times the printing pitch.
By using this amount to adjust the position where the print timing occurs, automatic adjustment of the print position during reciprocating printing is performed with a resolution of 1/4 of the pitch of the rotary encoder that detects the print position. The present invention makes it possible to perform print positioning during reciprocating printing, which is similar to when using an expensive linear encoder.

[Brief explanation of the drawing]

FIG. 1 shows a configuration diagram of a printer having an automatic print position adjustment function according to the present invention. 13, 14, 15, 1
6 indicates a paper feeding section of the printer. FIG. 2 is an explanatory diagram showing the output signal of a rotary encoder coaxially attached to a drive motor for detecting the position of the printer and the position on the printer. FIG. 3 is an explanatory diagram of the one shown in FIG. 2, taking into consideration the backlash of the drive gear and the extension of the rope (or belt). FIG. 4 shows a circuit of an embodiment of the present invention.
55 is a mono multivibrator for generating a timing signal at the edge of the digit.

Claims (1)

[Claims] 1. A carriage that is driven back and forth with respect to recording paper;
In a serial printer having a print head mounted on the carriage, a reset detector for detecting a home position, a first signal synchronized with the movement of the carriage, and a 1/4 pitch relative to the first signal; an encoder that outputs a second signal with a phase shift; and a counter that detects changes in the output of the encoder and adds and subtracts; the cartridge is made to stand by at the home position before the printing operation; The carriage is driven in a first direction away from the home position, and when the reset detector outputs a signal indicating that the carriage is away from the home position, the counter is initialized, and the change in the first and second signal output levels is set to a predetermined value. Then, the carriage is driven in a second direction opposite to the first direction to cause the counter to perform a subtraction operation, and when the reset signal outputs a signal indicating the home position, the counter is stops the operation of the counter, sets the count value of the counter to a correction value α, and when printing in the second direction, the first
A printing position adjustment method for a serial printer, characterized in that a print timing signal generated based on the signal is corrected by the correction value α to obtain a print timing signal.